Aircraft control system and method for reaching a waypoint at a required time of arrival

摘要

A method and apparatus includes long term and short term strategies for improving 4D trajectory reliability and required time of arrival reliability. The long term strategy changes speeds along the trajectory to remove the time error in predictions. The short term strategy compensates for wind and position error, for example, by temporarily changing an aircraft guidance speed by applying a guidance margin that would either delay or prevent re-computation of the speed targets along the flight path. The predictions would use the original speed target without the guidance margin application. The guidance speed target will stay applied until the predicted time error crosses a threshold.

主权项

1. A method for providing reliability for both a four dimensional trajectory of an aircraft along a path to a waypoint and a required time of arrival (RTA) at the waypoint, the aircraft including a flight management system processor including a trajectory predictor and an RTA solver, the method comprising:
enabling, by the flight management system processor, a temporary speed correction that compensates for unpredicted environmental errors in addition to a long term speed profile, the enabling step including:
computing, by the trajectory predictor, a time error as a difference between an estimated time of arrival (ETA) and the RTA without use of a guidance margin, wherein the guidance margin is a target speed modification that would delay or prevent re-computation of the long term speed profile along the trajectory;setting, by the flight management system processor, a guidance speed as the target speed required to reach the waypoint at the RTA plus an updated guidance margin;computing, by the RTA solver, the guidance margin to delay or prevent a long term speed profile computation and reach the waypoint at the RTA if the time error exceeds an interval determined by a first positive time threshold and a first negative time threshold, which change in magnitude as the distance to the waypoint decreases;setting, by the RTA solver, a guidance margin to zero and setting the guidance speed to equal the target speed plus the guidance margin if a time error reduces under a second positive time threshold and a second negative time threshold;repeating from the computing of the time error.